So, this am pH 8, FC >>5. Pressure at filter and water appearance unchanged.
Slowed return by approx. 50% by adding more DE (used an additional 1/3 cup).
Water began clearing. Vacuumed to filter until began to come out of return.
Backwashed when psi increased and flow slowed-rust in discharge.
Then added 1 cup each DE and polyquat. 1 cal-hypo in each basket.
Will check in am.